Winterfylleth is a compound of „winter" and „full moon": with the full moon of this month, by Anglo-Saxon reckoning, winter begins – the time of the Winter Nights.
Name & Meaning
Bede explains the invented compound: „winter full-moon", because with the full moon of this month winter takes its beginning. This matches exactly the Norse Vetrnætr, the Winter Nights. German Gilbhart (wine-moon) names the yellowing of the leaves and the vintage.
Work & Custom
Winter begins: the last harvest (fruit, roots) is brought in, the cattle taken from pasture into winter quarters, the pigs driven into the woods for the acorn mast. Into the Winter Nights fall the Álfablót and the Dísablót, household feasts for ancestors and guardian spirits. For many the new year begins here.
Bede’s Testimony
Winterfylleth can be named by the compound „winter full-moon", because with the full moon of this month winter takes its beginning.
— Bede, De temporum ratione ch. 15.
Sources
Bede, De temporum ratione ch. 15; Old Icelandic Vetrnætr (Winter Nights, Dísablót/Álfablót).